Effects of Temperature (0° to 150°C), Ion Association and Solvent Compressibility on Apparent Molar Volumes of Electrolytes

[Truncated] Data were obtained at 298.15 K on the apparent molar volumes of 25 electrolytes in N-methylformamide, formamide, propylene carbonate, acetonitrile and water by using two sizes of dilution dilatometer over a wide concentration range and by vibrating densimeter for liquid sulphur dioxide solutions. These results are discussed in terms of additivity, conformity to the Debye-Hückel limiting law and ion-pairing.
Of the bulk of the dilatometry data only electrolytes in acetonitrile showed,any significant deviations for the Debye-Hückel limiting law. These anomalies were attributed to ion-pair formation so association constants and volume changes on ion-pairing were calculated by two different fitting procedures for eleven electrolytes. To test this purely volumetric method of evaluating association constants a similar fitting procedure was used on aqueous MgS0₄ data for which reliable association constants and some volume change on ion-pairing information is available. The results show that the association constant and ion-pairing volume change were comparable with literature values.